The relatively low plasma cholesterol concentrations of vegetarians would be expected to reduce the risk of CHD. The first epidemiological study of CHD in vegetarians was published by Phillips et al.76 They reported that the risk of fatal CHD was three times greater in non-vegetarian than in vegetarian Seventh-Day Adventist men aged 35-64; the difference was smaller for older men and for women, but in the same direction. The lower risk in vegetarians was partly due to differences in other risk factors, such as smoking, hypertension, and exercise, but substantial differences in mortality remained after adjusting for these risk factors.
Data on mortality rates in Western vegetarians are available from the early study reported by Phillips et al.76 and from four other cohort studies that included a large proportion of vegetarians. Two of these studies were conducted among Seventh-Day Adventists in California, two among members of the Vegetarian Society and others in Britain, and one among the readers of vegetarian magazines in Germany. A pooled analysis of original data from these five cohort studies was published recently48,52 and included data for 76,000 men and women (of whom 28,000 were vegetarians). Importantly, the vegetarians and the non-vegetarians in each study had a shared interest in healthy living or a similar social/religious background. All results were adjusted for age, sex, and smoking, and a random effects model was used to calculate pooled estimates of effect for all studies combined. Further adjustments for body mass index, alcohol consumption, exercise, and education level had little effect on the results. There were 2264 deaths from CHD before age 90. In comparison with non-vegetarians, vegetarians had a 24% reduction in mortality from this disease (death rate ratio 0.76, 95% confidence interval (CI) 0.62-0.94). The reduction in mortality was greater at younger ages: death rate ratios were 0.55 (95% CI 0.35-0.85), 0.69 (95% CI 0.53-0.90) and 0.92 (95% CI 0.73-1.16) for deaths from CHD at ages <65, 65-79 and 80-89 respectively. The reduction in mortality was confined to vegetarians who had followed their current diet for more than 5 years. When the non-vegetarians were divided into regular meat-eaters (who ate meat at least once a week) and semi-vegetarians (who ate fish only or ate meat less than once a week), the CHD death rate ratios compared with regular meat-eaters were 0.78 (95% CI 0.68-0.89) in semi-vegetarians and 0.66 (95% CI 0.53-0.83) in vegetarians (test for trend P<0.001) (Figure 3.2).
Diet group CHD deaths Death rate ratio & 95% confidence interval
Regular meat eater 912 1
Figure 3.2 Pooled analysis of mortality in vegetarians and non-vegetarians: death rate ratios (& 95% confidence intervals) for CHD by diet group, relative to regular meat-eaters, adjusted for age, sex, and smoking, and for study using a random effects model. (Adapted from Key et al.48)
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